The worldwide in-building coverage market (IBW), or Distributed antenna system (DAS), as it is frequently called, has been constantly growing in the past few years. It is quickly becoming the major arena in which mobile operators' revenues are generated. Most of the calls and data transfers are now generated inside buildings and constitute around 80% of the operators' revenues.
In parallel to that, and due to the intensive use of smart phones, tablets, etc., data carrying capacity is quickly becoming a valuable and scarce resource. The demand for capacity has been constantly growing at a huge rate of around 100% per year. This means that a DAS system installed today will require twice the capacity a year from now and will require 8 times more capacity three years from now.
The aforesaid facts are valid not only for indoor DAS but also for outdoor DAS's particularly when serving multiple operators in confined areas such as campuses, stadiums etc.
Current indoor and outdoor DAS systems are predominantly coverage centric. The capacity is evenly and rigidly distributed and is not dynamically controlled as one would expect from such a valuable scarce resource. Any growth in capacity or reallocation of capacity requires a major redesign of the DAS system and a change of installation. It is difficult to integrate multiple technologies and multiple operators while making the DAS provide a cost effective specific frequency response (transfer function) for each technology and each operator. Trying to locate a mobile user inside a building or a campus is almost impossible since there are no GPS signals inside buildings.
Thus, there clearly is a need for a DAS addressing the current needs of DAS systems.
Adapt the DAS to Meet Continuously Growing Demands for Capacity
Since the demand for capacity has been constantly growing and is expected to grow even more in the future, there is a need for a DAS with a flexible architecture that will provide the ability to easily and constantly adapt to the growing demand for capacity without the need to perform major redesigns and changes in installations.
Easy Integration of Multiple Wireless and Broadband Technologies
There are now multiple technologies dealing with the capacity issue such as 3G/4G and other broadband technologies such as Small Cell and Wi-Fi that enable offloading of capacity from the macro cellular networks. There is a need for a DAS that will be able to easily and cost effectively integrate all these technologies into one system while still providing an individual frequency response (transfer function), specific routing scheme, and power level to each technology, each frequency sub-band, and each operator. There is a need to be able to differentiate between the various technologies so that the system can route specific cell resources of specific technologies to certain locations in the building where capacity is currently needed.
Dynamic Capacity Allocation
Current DAS systems are predominantly coverage centric. The capacity is evenly distributed across the entire building/campus area. Current approaches to addressing this need rely on installing “small cells” as close as possible to the mobile user. This generates small coverage spots and enables a reuse of spectral resources. However this way of distributing capacity is rigid and once capacity is allocated there is no way to reallocate capacity from one location to another except without reinstalling the small cells.
Since the demand for capacity is not always static, both in the time domain and also in the location domain, it becomes prudent to adopt a new approach which deals with the scarce capacity resources as a common pool of resources which can be transferred to wherever is currently mostly needed. In a way, it is similar to queuing theory in which all customers are forming one queue and whenever there is a resource available a customer is directed to this resource. This approach of treating the resources as one pool is far more efficient than generating several “queues” as used to be in the past. The central pool of capacity may also take into consideration the various offload devices installed in the building when allocating capacity to various zones in the building.
In Building Location Based Services
The need to locate a mobile user has two reasons.
1. Security reasons—Many countries are now mandating that the operator should be able to locate the mobile user when the user dials E911 or an equivalent number.
2. Commercial reasons—The operators want to leverage the location information in order to broadcast advertisements, promote sales etc.
Location finding can be easily achieved when the user is outdoors, particularly nowadays when most mobile phones are equipped with GPS devices. However this capability cannot be achieved inside building areas in which no GPS signals are available. The operator may know that the mobile user is in the building/campus based on a BTS report, however he cannot tell in which floor or area he is in. There is a need to locate the user to a greater accuracy.
Preventing Cellphone use in Certain Building Locations
In certain buildings or outdoor environments, there is often a need to mask or jam certain areas so as to prevent the users from generating calls in those specific areas, while at the same time enable calls in other areas of the building or the outdoor environment. This need may occur in theatres, cinemas, hospitals, prisons, schools with exam rooms, etc.